1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a method for coating polyimide on a liquid crystal display panel.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal display panel and a backlight module. The operation principle of the liquid crystal display panel is that liquid crystal molecules are interposed between two parallel glass substrates and electricity is applied to the glass substrates to control variation of orientation of the liquid crystal molecules in order to refract light emitting from the backlight module for generating images.
A liquid crystal display panel is generally composed of a color filter substrate, a thin film transistor (TFT) substrate, and liquid crystal (LC) and sealant interposed between the CF substrate and the TFT substrate. A general manufacturing process comprises a front stage of array process (including thin film, yellow light, etching, and film stripping), an intermediate stage of cell process (including bonding TFT substrate and the CF substrate), and a rear stage of assembling process (including mounting drive ICs and printed circuit board). The front stage of array process generally makes the TFT substrate for controlling the movement of liquid crystal molecules. The intermediate stage of cell process generally introduces the liquid crystal between the TFT substrate and the CF substrate. The rear stage of assembling process generally integrates the drive ICs and the printed circuit board to drive the liquid crystal molecules to rotate for displaying images.
A liquid crystal display panel often needs to coat polyimide (PI) on the TFT substrate and the CF substrate and to apply rubbing or photolithography on the polyimide to form pre-tilt angle to provide liquid crystal molecules with a supporting angle.
Referring to FIG. 1, for the conventional operation of coating polyimide, it generally uses rollers 150 to uniformly distribute a solution of polyimide 170 on a relief printing plate (Asahikasei Photosensitive Resin, APR) 130 and then transfers the polyimide solution 170 from the relief printing plate 130 by means of the rollers 150 to a TFT substrate or a CF substrate 110, while the TFT substrate or the CF substrate 110 is moving in the direction indicated by the arrow so as to complete the coating operation of the polyimide solution 170. However, the known polyimide coating device is relatively complicated and the operation time of coating polyimide is long. Thus, both the coating device and the coating operation are needed to be further improved.